Diagnostic cytology has been used extensively as a detection system for alterations in cellular morphology, such as alterations which may occur when a normal cell develops into a cancerous cell. One of the main applications of diagnostic cytology is in the early detection of cervical cancer. For over three decades, the Papanicolaou (PAP) smear has been used as a routine screening procedure for neoplastic and pre-neoplastic cells isolated from the cervix uteri. Neoplastic cells generally refer to benign transformed cells (tumor cells) and malignant transformed cells (cancerous). Recently, however, national controversy has surrounded the accuracy of PAP smear testing. Statistics indicate that as high as 50% of all PAP smears performed may result in false negatives due to sampling error. This statistic reflects that while many women may be diagnosed as normal at the time of testing, they may actually have pre-malignant or malignant cells that are incorrectly sampled or incorrectly evaluated. Thus, a statistically significant number of mortalities occur from cervical cancer due to inadequate testing techniques.
The principal aspects affecting the accuracy of PAP smears are the reliability of the cell sampling techniques used and the skill of cytotechnologists to accurately evaluate and report the cell sample analysis. Accurate and meaningful results can only be obtained if the cell sampling technique is efficient with respect to the collection, fixation and staining of desired cells. Thus, the potential for error in the sampling and evaluation stages of conventional procedures has prompted the need for improved standardization of PAP smear collection methods and devices.
Prior attempts have been made to standardize the interpretation of collected cells. Several automated cytological specimen screening devices are commercially available that will allow healthcare workers to pre-screen the cytological specimens, thus providing some degree of standardization with respect to the parameters used to classify cells as normal or abnormal. Because such automated devices address solely h problem of unreliable cell sample analysis, there remains a need to address the significant problems encountered in the collection and preparation of cell samples.
Cell samples are typically removed from the mucous membrane of the cervix uteri by scraping the tissue with a spatula or a cotton swab. Once collected, the cell sample is smeared onto a glass plate or slide, sprayed with a conventional fixative, stained, mounted with a coverslip, and examined under a microscope. A major problem in performing PAP smears in this manner is that any cells that are exposed to air before being fixed assume morphologies that are distorted and difficult to evaluate. One of the predominant characteristics of an abnormal cell is its relationship of the nucleus to the cytoplasm and the ability of evaluating the DNA content of that nucleus. Morphological changes to pre-cancerous or cancerous cells can be artifactually masked by artifactual distortion caused by exposure of the cells to air, such distortion making cancerous cells appear to be normal resulting in false negative PAP smear tests. The problem caused by morphological changes resulting from exposure of collected cells to air is exacerbated when, as is often done, multiple samples are obtained from different anatomic sites of a patient prior to the fixation of an individual cell sample obtained from any one particular sample site.
In addition to inaccurate PAP smear results caused by exposure of cell samples to air, false negative tests often result from sampling an inadequate number of particular endocervical cells. It is known that there is a "transformation zone" where columnar cells transform into squamous cells. If a sufficient number of cells are not sampled from this "zone", then neoplastic cells may go undetected.
Prior investigators have taught the use of various devices for the collection of cells from cervical uteri. These devices, however, do not adequately address the sampling problems described above. For example, U.S. Pat. No. 3,540,432 by Ayre, issued Nov. 17, 1970, describes an instrument for sampling cervical tissue. The instrument comprises, a pipet containing glycerol and a bulb attached to one end of the pipet. In a two-stage process, cells are collected by squeezing the pipet bulb and releasing it while scraping the head of the pipet along the tissue. Ayre discloses that some cells are drawn into the pipet while others remain outside on the pipet head. Cells are then transferred from the instrument into glycerol contained in a cap by squeezing the attached pipet bulb thereby expelling the cells by air. Cells can be collected in the instrument at home and then mailed to a laboratory for cytological analysis. U.S. Pat. No. 4,620,548 by Hasselbrack, issued Nov. 4, 1986, describes an elongated spatula for scraping and collecting cells. The spatula is attached to a bulb or syringe. Cells are collected into the aspiration tube by squeezing the attached bulb. The attached bulb is again squeezed to eject the cells by air onto a microscope slide. The leading edge of the spatula is then rubbed in the pool of ejected cells to remove cells remaining on the outside of the spatula. The cells are then spread across the face of a glass slide, and finally fixed using a conventional spray-type fixative. U.S. Pat. No. 4,633,886 by Bucaro, issued Jan. 6, 1987, describes a two-stage process using a device consisting of an elongated tube having a plunger and a separate chamber containing a fixative solution. Cells are drawn into the tube containing a preservative using the plunger and the tube is then interlocked with the separate fixative-containing chamber. The fixative is permitted to flow and mix with the collected cells.
Another major problem in performing PAP smears is the safe management of the cell sample when collecting cells from individuals potentially infected with HIV. With the onset of the AIDs epidemic, it has become critical that healthcare workers minimize their contact with human tissue and/or body fluids. The Occupational Safety and Health Administration (OSHA) has set forth extensive guidelines for protecting healthcare workers against the hazards of exposure to potentially infected human tissue and/or bodily fluids. Under OSHA regulations, human bodily fluids include semen, vaginal fluids, cerebrospinal fluid, synovial fluid, pleural fluid, pericardial fluid, peritoneal fluid, amniotic fluid, saliva, and any body fluid that is visibly contaminated with blood, and all body fluids where it is difficult or impossible to differentiate between body fluids. OSHA guidelines specifically indicate that all procedures involving blood or other potentially infectious materials shall be performed in such a manner as to minimize splashing, spraying, spattering, and generation of droplets of these substances and that specimens of blood or other potentially infectious materials shall be placed in a container which prevents leakage during collection, handling, processing, storage, transport, or shipping (29 U.S.C. 653 .sctn.1910.1030 (1991)). Conventional methods for collecting PAP smears requires direct contact with the tissue sample by post-collection manipulation of the tissue sample, thereby increasing the risk of contact with the tissue sample and/or body fluids.
To overcome the problem of healthcare worker direct contact with human tissue and/or body fluids, as well as the problem of inaccurate testing due to morphological changes of cell samples prior to fixation, it would be desirable to have a method and device that would allow sampling of cells in a system that prevents exposure of collected cells to air and alleviates significant exposure of healthcare workers to collected cells. Such a method and device would eliminate sampling errors and standardize means of evaluating cell samples, decreasing the number of false negatives, preventing undue exposure of healthcare workers to potentially infectious agents, and resulting in the saving of human lives.